In principle, other than at infantile age, fractures of long tubular bones are treated by surgery. To this end, a plate of metal or titanium is available on the one hand which, when the plate has been set and adapted to the bone geometry once the fracture has been exposed, can be attached to the bone in order to fix the fracture. On the other hand, intra-medullar stabilisers are being increasingly used, which are also available in different shapes. Medulla nails are also available for treating such fractures.
The fixing principle of such a medulla nail is based on an elastic clamping action between a “rigid” component (bone) and an elastic component (nail), as described in connection with medulla nailing in 1984 by Helms and Naseband in “Ingenieurwissenschaftliche Grundlagen der intramedullaren Osteosynthese” [Engineering principles of intra-medullar osteosynthesis]. The precursor to elastic medulla nailing was G. Küntscher, who tested numerous nail profiles in order to obtain optimum clamping of the nail in the medulla cavity of the bone. Some of these were different from the cylindrical shape of medullar nails used these days. Clover-leaf, triangular or lamellar-type configurations were used. Examples of these nail shapes were illustrated in “Praxis der Marknagelung” [The practice of medulla nailing] by G. Küntscher published in 1962 by Schattauer of Stuttgart. Other examples are illustrated in the journal “Unfallchirurg” [Emergency surgeon] No. 104 on pages 639 to 653 as part of the article published in 2001 entitled “Prinzipien der intramedullaren Knochenbruchstabilisierung” [Principles of intra-medullary bone fracture stabilisation] by C. Krettek. The common purpose of all these profiles is to impart the best possible elastic properties to the medulla nail. In principle, the inserted implant should make the bone fragments as resistant to tilting as possible due to the clamping action in the medulla cavity. This works well with fractures in the middle of the bone. Much more problematic, however, is a break at the bone end because the bone is wider there and less cylindrical in shape than in the middle of the bone. The farther the breaks occur from the bone middle, however, the wider the bone is and also the shorter the distance on which clamping can take place. Another problem is the fact that these implants are not very resistant to torsional forces.
As a result, this shape of elastic medulla nail has been largely abandoned these days, giving way to the use of rigid, less elastic, usually solid nails. The technique currently used as standard for shaft fractures as well as for fractures outside of the middle of the shaft involves inserting a rigid nail from a readily accessible part of the bone which is remote from a fracture. The nail is pushed into the remaining fracture beyond the fracture end and is so as far as the end of the bone. In order to obtain the best possible resistance to axial compression stress and above all stress caused by rotation, the nails are locked on both sides of the fracture, as explained in the above-mentioned article by C. Krettek published in the journal “Unfallchirurg”. To achieve this locking effect, the nail has bores extending through the entire diameter and screws serving as locking bolts are introduced firstly into the bone and then inserted in the nail. This is done without the person carrying out the operation having direct sight because the nail is already disposed in the inner region of the bone. In order to find the lock bores, guide fixtures which are calibrated by the manufacturer for the specific nail type, are used as a template, as illustrated in FIG. 3. These guide fixtures are fixedly connected to the beginning of the nail, making it at least possible to find the nail bores at the beginning of the nail. In practical terms, however, this has not been possible using guide fixtures because even a rigid nail bends slightly as it is being introduced into the rigid bony medullary canal.
As a result, these bores in the nail end have been located by viewing them with the aid of intra-operative X-ray imaging in the prior art. This involves a certain amount of X-ray exposure for both the patient and the surgeon and costs valuable time. The prior art described above is explained in the paper published in 2001 in the journal “Radiologe” [Radiologist], No. 411 on pages 91 to 94 entitled “Radiation exposure of the patient by intraoperative imaging of intramedullary osteosyntheses” by N. Suhm, A. L. Jacob, I. Zuna, H. W. Rosner, P. Regazzoni and P. Messmer. If a medulla nail is inserted but not locked, however, it is not possible to obtain sufficient resistance to compression and above all to rotation.